[Battery and charging Q's]

Hello all' I may be new to kedron but am certainly familiar with PL20 Plasmatronics and have been using this unit for a long time and it is excellent. My comment however, refers to batteries and in particular discovering successful ways to desulphate batteries that are getting tired, and there is circuitry about that enables this that actually works and I have made six of these units now and when used in conjunction with a genuine old style 2 amp trickle charger work very well in my experience. These units work off battery voltage directly and have an led that lights up and use about 300-700 milliamps/hour during operation. If anyone is interested in doing this I will cheerfully direct those handy with a soldering iron where to buy the kits from and the mods that can be made for more muscle if required. If used regularly as a preventative measure [not connected all the time-not necessary] battery life can be extended significantly and if used in conjunction with 1. an accurate specific gravity reader and 2. a battery tester [100 amps shorting load for 10 seconds] you can find out how well the desulphator is working over a period of days or longer by testing the battery directly. I am at present making a variant that has a built in idiot proof on/off switch [it does matter which lead is put on first but correct switch wiring removes this possibility] and a low amp trickle charger that should be switched on after the unit is started and the red led lights up [which means its working and there is also a humming sound as well. I am happy to email this info if asked to do so. Cheers. Mark Email me

[Battery and charging Q's]

Pete and Tracey

From the point of view of a retired Electrical Engineer who has designed and run solar power systems for 20 years or more - a couple of points.

The difference between the open circuit solar panel voltage and the MAX voltage or system voltage you are reading at the end of the day is the potential difference available to drive current into your battery bank. Don’t bother about it, leave that to the regulator.

As the operator of the system on your Kedron watch two things.

State of Charge (SOC) and MIN system voltage.

Today’s small solar regulators are really Programmable Logic Controllers, called PLCs. In essence they consist of a bunch of counters fed by voltage sensors. To get to the SOC reading the PLC counts the Amp Hrs IN and the Amp Hrs OUT and adds em up. The SOC even though it has some inaccuracies is a fairly useful figure if you watch it over time, say a week or two. Interestingly if you read SOC one can at times see a figure above 100%, the Plasmatronic regulators can read up to 127%. How I hear you ask can a battery bank be measured at 127% of its rated capacity. The answer is that there are daily inaccuracies in the adding of the IN and OUT values that allow the figure to creep up. With the Plasmatronic regulators, hold the button for five seconds while reading SOC and the SOC figure will reset to 100%. Other brand regulators have resets as well.

Probably the most important thing about batteries is that to operate them in a deep cycle mode i.e. use a large portion of their rated capacity will unfailingly lead to a short battery life. This comment applies to all batteries, deep cycle included. I have 3 X 120A/Hr batteries in our Kedron so my overall capacity is 3X120=360 A/Hr. However when the SOC reads 75% I start the generator. So in other words even though I am towing around 360A/Hrs of capacity I only am prepared to use 25% of that or 90A/Hrs. When the van is parked up I use a trickle charge. Operating this way should give me good battery life.

As a backup measure of how the batteries are holding up watch MIN volts on your controller. On a typical Kedron setup it should almost never drop below 12V. An almost dead flat battery will quite happily read 12V with a multimeter across the terminals. One has to ask the same battery to deliver a substantial current and then read the resultant terminal voltage to detect a discharged or sulphated battery. It is called load testing. If you are seeing 11.6 or 11.8V at night after the evening load save up for buying new batteries.

Your panels at 4 X 130W have the theoretically capacity to deliver 43 Amps to the regulator, but they won’t do that. The efficiency of solar panels is highly dependent on their temperature. By the time the sun is well overhead they are quite warm and their efficiency will have dropped considerably. As a last point I will mention Peukert’s Law which has the effect of reducing the energy available from a battery. The conversion of an electric current form of energy to a chemical form of potential energy and then back to an electric current has a cost. The cost is described by Peukert’s Law. As a rule of thumb work on 90 to 93% of available solar output being available back at a load such as your DC light in the caravan.

In short monitor your SOC fairly closely, and more often during poor solar weather and use MIN voltage as a important backup indicator.

I hope this ramble is helpful.

Grahame